From an early age I have always loved dinosaurs, and Triceratops was my favorite. Now there apparently is a scientific debate raging on whether those viscious-looking horns were primarily ornamentation that served a social function (attracting mates, establishing social heirarchy among rivals), or weapons used to defend against predators. Indeed, the hypothetical battles between Triceratops and Tyrannasaurus occupied much of the imagination of many a young dinosaur enthusaist, and arguments raged as to who the victor would be. I'm no paleontologist, but my impression of the outcome given their relative sizes and what I know of predator/prey behavior, is that a T-rex probably would not risk attacking a Triceratops that was full grown and not ill, because the risk of receiving a life-threatening gore would be too high, even in victory.
Now the science apparently tells a much lesss violent story, for much as I prefer the other interpretation, the data seems to support pretty strongly that those spike are ornamentation to intimidate rivals and attracts mates. Particularly persuasive to me was the fact that the frills triceratops and his relatives grow on their head may look like shields, but were actually too thin to be any problem for T-Rex teeth.
Hat tip to Grrlscientist for